The present invention relates generally to an optical module which is used for the purpose of distance measuring, focus detecting and others, and in particular to an art for downsizing the module consisting of a pair of optical systems and a pair of sensors. Further, the invention relates to a distance measuring device having the module, and also an apparatus such as a camera, an image processing apparatus or a measurement device having said module.
An example of a conventional module which is used in a light-passive method (what is known as the AF sensor) is explained in FIGS. 5(a) and 5(b). As shown in these figures, the module comprises optical system 51 which consists of a pair of horizontally aligned lenses, and line sensors 52a and 52b. In the module constructed in this manner, however, an object distance can not be measured in case of the absence of contrast in a baseline direction, (e.g., the horizon etc.). This case is shown in FIGS. 6(a) and 6(b). FIG. 6(a) shows a photographic image plane in which the horizon is positioned in the baseline direction. In such a case, as shown in FIG. 6(b), an output from the line sensor has no changing component, hence it is impossible to measure the object distance. In order to solve such a problem, a module shown in FIGS. 7(a) and 7(b) consisting of two pairs of optical systems 51 and two pairs of sensors 52a, 52b, 53a and 53b, which are aligned vertically to each other, has been provided. In such a structure, contrast of an object is obtained in both of the vertical and horizontal directions, which makes it possible to measure object distance. This method is shown in FIGS. 8(a) and 8(b). In such a manner, although it is impossible to measure the object distance on the basis of output from the line sensor A (line sensors 52a and 52b), it is possible to measure the object distance on the basis of output from the line sensor B (line sensors 53a and 53b). In FIGS. 6(a) and 8(a), since line sensors in each of the pairs detect the same area in the photographic image plane, each of pairs of line sensors is depicted as one line sensor in the figures.
However, as shown in FIGS. 7(a) and 7(b), in the above-mentioned conventional module employing two pairs of optical systems and two pairs of sensors, one pair of optical systems with line sensors are aligned horizontally, and another pair of optical systems with line sensors which are aligned vertically, so the space or size of the module is increased. Therefore, in the case of mounting the module in a camera, the camera may not contain a part 56a of the module 56 inside a camera housing 55, or there may come a dead space 57. Moreover, there has been a problem that the camera in which the module 56 is mounted, is upsized.